Friendly Flatworms: The Temnocephalida

Andrew Hosie's blog | Created 3 years ago

We recently had a phone call from a curious citizen, Andrea Davy, who had noticed that the yabbies and marron in one of her ponds were crawling with some very strange animals. Fearing some kind of parasitic invasion she brought them to the Museum for identification.

Known as temnocephalids, these belong to a group of mostly free-living, non-parasitic flatworms known as the rhabdocoel turbellarians. Unlike the free-living flatworms, the temnocephalids have a sucker located on the underside of the body. They are known to attach to freshwater crustaceans, particularly crayfish, and can be found around the world. This particular species is most likely Temnosewellia minor a worm that is native to New South Wales and Victoria but was introduced into Western Australia and around the world when yabby farming took off, sometime after the 1960s. There are only two native Temnosewellia species in southern Western Australia, but on the east coast, however, there are >30 known species, some of which have been found in only a single tributary or on a single species of crayfish.

While these curious little worms do look a bit like a disembodied hand or Thing from the Addams Family, they’re nothing to be afraid of. They attach themselves to the crayfish with their surprisingly strong sucker, usually under the tail and use their finger-like tentacles to capture food. They aren’t feeding on the crayfish but are opportunistic, feeding on other small organisms, like nematode worms and protozoans, that get stirred up by the crayfish. When they’re on the move, they use their ‘hand’ to reach out and pull themselves along, as can be seen in the video below.

Special thanks to Dr. Kim Sewell at the University of Queensland who helped with the information and identification.